An icy retreat

It’s almost routine by now: Every summer, many of those interested in climate change check again and again the latest data on sea-ice evolution in the Arctic. Such data are for example available on a daily basis from the US National Snow and Ice Data Center. And again and again in early summer the question arises whether the most recent trend in sea-ice extent might lead to a new record minimum, with a sea-ice cover that will be smaller than that in the record summer of 2007.

However, before looking at the possible future evolution of Arctic sea ice in more detail, it might be a good idea to briefly re-capitulate some events of the previous winter, because some of those are quite relevant for the current state of the sea-ice cover. The winter 2009/2010 will be remembered by many people in Europe (and not only there) as particularly cold, with lots of snow and ice. Not least because of the sustained cold, some began to wonder if global warming indeed was real.

Such questioning of global warming based on a regional cold period of course neglects the crucial difference between weather and climate, with the former being the only thing that we as individuals will ever be able to experience first hand. A single regional cold spell has not a lot to do with climate – let alone with global climate. This becomes quite obvious if one instead considers the mean temperature of the entire globe during the last 12 months: this period was, according to the GISS data, the warmest 12-month period since the beginning of the records 130 years ago. Regarding sea ice, it was particularly important that temperatures in parts of the Arctic were well above average for most of the winter. This was directly experienced by some members of our working group during a field experiment at the West Coast of Greenland.

Fig. 1: Temperature anomaly at 1000 hPa during the first half of January 2010 with respect to the period 1968-1996. Warm anomalies in the Arctic and cold anomalies in Northern Europe and parts of North America are clearly visible.

The initial plan of this field experiment was to study the growth and decay of sea ice in great detail throughout an entire winter. In particular, we wanted to focus on the evolution of very young sea ice that had just formed from open water. Therefore, we wanted to start our measurements just before initial ice formation, which usually takes place in mid-November, at least according to past experience of the local Greenlandic population. Hence, we traveled to our measuring site close to the Greenlandic settlement of Upernavik in early November to put out our measuring buoys. We were hoping that ice formation would start shortly after we had put out the instruments such that they were protected from storms and waves. However, with temperatures that were often more than 10°C above the long-term mean, sea ice was nowhere to be seen. Even in January, there were days on end with above 0°C temperature and heavy rain fall. Finally, in February a stable ice cover formed, which of course remained relatively thin and which hence had melted completely by mid May.

The fact that it was sometimes warmer at our measurement site at the West Coast of Greenland than it was in Central Europe at the same time surprised us quite a bit. However, some recent studies indicate that such a distribution of relatively high temperature in parts of the Arctic and relatively low temperature in Northern and Central Europe and parts of the US might become somewhat more wide-spread in the future. While the Arctic has always shown large internal variability that lead to large-scale shifts in weather patterns, in the future the ongoing retreat of Arctic sea ice might cause those weather patterns to occur more often that allow for Northerly winds to bring cold air from the Arctic to the mid-latitudes. Hence, it is quite possible that because of the retreat of Arctic sea ice, some smaller parts of the Northern Hemisphere will experience pronounced cold spells during winter every now and then. The mean temperature of the Northern Hemisphere will nevertheless increase further, and the export of cold air from the Arctic of course leads to warm anomalies there.

Fig.2: Evolution of Arctic sea-ice extent from September 2009 until mid May 2010. The blue line denotes the mean extent from 1979 until 2000, while the shaded region denotes the variability during that time (± 2 standard deviations)

But let’s return to the evolution of Arctic sea ice. Because of relatively high temperatures, Arctic sea-ice extent remained well below the long-term mean for most of the preceding winter. However, in March temperatures suddenly dropped for a couple of weeks, in particular in parts of the Barents Sea and in parts of the Beaufort Sea. This in turn lead to the formation of a thin ice cover in these regions, which caused a marked increase in observed sea-ice extent. For the measurement of this extent, it doesn’t matter at all how thick the ice is: any ice, however thin, contributes to sea-ice extent. Therefore, only considering a possible “recovery” of just the extent of Arctic sea ice always remains somewhat superficial, since sea-ice extent contains no information on the thickness of the ice. A much more useful measure for the state of Arctic sea ice is therefore the total sea-ice volume. However, for its estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.

Fig.3: Evolution of Arctic sea-ice extent since April 2010 in comparison to 2007 and 2009. The blue line denotes the mean extent from 1979 until 2000, while the shaded region denotes the variability during that time (± 2 standard deviations)

Because of the very low thickness of much of the Arctic sea ice, it wasn’t too surprising that at the end of the winter, sea-ice extent decreased rapidly. This rapid loss lead up to the lowest June sea-ice extent since the beginning of reliable observations. After this rapid loss of the very thin ice that had formed late in winter, the retreat slowed down substantially but the ice extent remained well below the long-term mean. Currently, the ice covers an area that is slightly larger than the extent in late July of the record year 2007. However, this does not really allow for any reliable projections regarding the future evolution of Arctic sea ice in the weeks to come.

The reason for this is mostly that sea ice in the Arctic has become very thin. Hence, in contrast to the much thicker ice of past decades, the ice now reacts very quickly and very sensitively to the weather patterns that are predominant during a certain summer. This currently limits the predictability of sea-ice extent significantly. For example, in 2007 a relatively stable high-pressure system formed above the Beaufort sea, towards the north of North America, leading to rapid melting of sea ice there. If again such stable high pressure system forms in the Arctic throughout the coming weeks, we might well experience a sea-ice minimum that is below the record minimum as observed in 2007. However, if the summer should turn out to be colder than during the previous years, a sea-ice minimum similar to that observed in 2009 would not be too surprising. Hence, at the moment all that remains is to wait – and to check again and again the latest data of Arctic sea-ice extent.

Fig.4: Arctic sea-ice extent on June 28July 20, 2010. The orange line denotes the mean extent on June 28July 20 from 1979 until 2000.

Dirk Notz is head of the research group “Sea ice in the Earth System” at the Max-Planck-Institute for Meteorology in Hamburg.

The original version of this article was published in German at KlimaLounge

John P. Reisman (87), I was merely pointing out that Dirk Notz says (and Tamino mostly agrees) that are ability to measure ice thickness is very poor — near nonexistent with any credibility, and that there is a bit of a cognitive disconnect with your-all’s “solid confidence” that ‘we know anyway that it is getting very much less.’ Like lets not let little nuisances like measuring things hinder our positions.

Kevin Stanley (91), the statements 1) …the overall distribution of ice thickness, which we have not been able to measure routinely in the past…, and 2)…data show beyond doubt that the ice is a lot thinner now than previously… are consistent with each other??? Could’ve fooled me! I wonder how much “a lot” is, especially “beyond doubt.”

I think it is perfectly and scientifically reasonable to assume that as sea-ice extent diminishes, thickness probably does to — to some extent. That is not what I was fussing about.

Since this comment will be at the start of a new page, and the comment starting the last page—#51—noted that current sea ice loss is consistent with IPCC modeling for 2050, I’d like to hear thoughts about the “why” of this that methane defines.

As I have commented before at RealClimate, it appears that methane concentration tends to be peaking in the high northern latitudes in conjunction with late December and early January—the onset of the hard freeze. If the amount of insulation in the atmosphere is increasing (in the last decade it would appear that the Arctic has seen a 50 ppb increase of its average, and the seasonal variation seems to also be about 50 ppb), and countering what Gavin has asserted about the importance of methane relative to carbon dioxide, it seems to me that in the high northern latitudes, and at a time when early ice extent recovery is critical to facilitating lower temperatures as winter progresses (and retaining sea ice), this added insulation could be a key part of what the models have missed when missing when the kind of summer sea ice loss we are experiencing should have been expected to occur as the planet warms.

I have been trying to see the signature of the increased methane in the ice data. I am now wondering if it is the rapidly growing area of ~60-80% ice ‘flowing’ through the center of the ice cap observable in this season’s melt that is the summer’s aspect of it, while the balance of the signature is visible in Figure 2 in the difference in the shape and height of the winter curves.

Temperature increase is a root cause of the change in both extent and volume. As a former insulation contractor I know that increasing insulation—due to the logarithmic nature of U values—has exponential impacts relative to heat loss. More insulation of a type as potent as CH4 occurring in the atmosphere during the onset of ice formation is a significant variable that I am not reading discussion about in either this post or its comments. Have I missed anything?

Part of why I Photoshopped the 1979-2000 curve as I did in my prediction this year—see #19—is that I was factoring in an educated guess re what methane is causing. As I noted before, that curve of the average is defined, primarily, by extent decline at the edges of the Arctic ice. If methane’s added insulation effects the winter dymics more than the summer ones, and the center of the ice cap more then its edges, such is a dynamic that I am betting is poorly modeled. Is this possible? It also seems to me that with the increasing loss of ice volume, the extent becomes an ever poorer stand-in for volume.

Such would certainly would seem to be the case in what has constituted this discourse in the bulk of these comments.

When the confusion resulting from conflating extent and volume is combined with the role motivated reasoning plays in public discourse, it seems to me that what is critical is to begin to include methane in what gets reported about the ice extent changes in the Arctic. Relative to comments about the southern hemisphere’s ice extent, there is a 100-150 ppb difference in atmospheric concentration of methane between the poles p://www.esrl.noaa.gov/gmd/ccgg/globalview/ch4/ch4_intro.html . And while Dlugokencky et al unhelpfully noted this winter that they could not see the signature of the methane time bomb’s detonation in the surface air sample analyses reported on for 2007 & 8, the metric was noted to not be a good one to see such. Concurrently, Bloom et al have used satellite data to extrapolate an increase in methane coming from the high northern latitudes. Heat loss and gain dynamics concerning the delay that the latent heat of water effects in what is observed in sea ice is key to understanding risks for which the Arctic is a metaphorical canary-in-the-coal-mine. Due to the heat involved in the change of phase of water, methane, as insulation, plays a much different role at the poles than it does elsewhere on the planet. In the Arctic, now, it is “all about (me)thane.”

The sooner the relative importance of is methane in the Arctic is commonly understood, the less unintelligent our society might act. Science-focused blogs, like RealClimate, seem like a good place to be doing this.

RodB said: “I think it is perfectly and scientifically reasonable to assume that as sea-ice extent diminishes, thickness probably does too”

And all the data we have supports this. What we lack is a continuous dataset, in both time and space. So, we know that ice is thinning. What we don’t know is if it was unusually thick or thin in specific years, or if it was unusually thick or thin in specific areas.

However, we can even estimate that information. We can track ice age and location, and that helps confirm estimates of thickness.

I know deniers always think we shouldn’t act until we have all the data, and everything nailed down “to ten points of decimals”, as Lord Flibbertigibbet would say. But in this one case, can’t we just agree that the boat has sailed? We can’t go back in time and fill in the gaps in our observations of thickness. We will have to make do with the historical records we have.

And, for the Nth time: the data we have supports the conclusion that ice has thinned significantly.

Rod B (in #101) talks about “cavalier back-of-the-hand throwing into the trash of the recent up ticks” in summer minimum sea ice extent. Everybody should look at the graph. The “recent up ticks” are utterly meaningless in regard to the declining trend.

I base that statement on examining and anlyzing the data. The last three years (which includes those two “up ticks”) are the three lowest on record, and are all well within the error range defined by the long-term trend. There is no evidence at all — zero, zip, nada, squat — of any “recovery” or “reversal” or doubt.

This is not a “cavalier back-of-the-hand throwing into the trash.” It’s statistics. Rod B is the one who is being cavalier. He’s throwing into the trash the long-term trend for no other reason than he doesn’t want to believe the obvious result. He has no evidence or analysis to back up his claim — zero, zip, nada, squat.

Rod B (in #103) also says “Dirk Notz says (and Tamino mostly agrees) that are [sic] ability to measure ice thickness is very poor — near nonexistent with any credibility.” What Notz actually says about sea ice thickness is that “we have not been able to measure routinely in the past” and in consequence “at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.” He also says “sea ice in the Arctic has become very thin,” which certainly implies that he has great confidence in the overall conclusion of an overall thinning trend. I agree with all his statements, and I’ve also posted about some of the evidence of thinning ice overall. This evidence consists of actual measurements, with credibility far exceeding Rod B’s estimation (or of Rod B himeself), and is only one piece in what’s emerging as an ever-clearer picture.

It’s clear that we don’t have anywhere near the consistent, complete coverage of sea ice thickness (either spatially or temporally) required to reconstruct either thickness or volume with the same precision we can gauge extent or area. But the claim that our ability to measure ice thickness is “nonexistent with any credibility” is utterly false, nothing more than wishful thinking on the part of Rod B because he doesn’t want to face the truth.

Until Rod B admits that he’s just plain mistaken on both these points, it’s time to recognize that his credibility is nonexistent.

Didactylos, most of what you say in #107 I don’t have a problem with. My point was that your precise words in 207 are not the same as “data show beyond doubt that the ice is a lot thinner now.” This might sound nit-picky but in scientific analyses nitpicks are important: do you fire the retro rockets for 11.5 sec or 12.5 sec? or more striking, do we fire them at X kilometers or X miles?

The idea that “deniers always think” we shouldn’t act until we have all the data (I’ll let this hyperbole pigeon-holing pass for the sake of discussion) doesn’t give you license to blow things way out of rationality — at least in scientific discussions… in political discussions maybe a little is O.K.

Tamino, except I read your post and noticed that you did NOT throw the recent up ticks into the trash in your analysis.

“…nonexistent with any credibility” might be an exaggeration (“nonexistent” is a bit too pure), but ‘very little with good credibility’ is pretty much the same thing you say about the data in #108: “…don’t have anywhere near the consistent, complete coverage of sea ice thickness (either spatially or temporally) required to reconstruct either thickness or volume…”

I have no basis or cause for disagreeing with your overall analysis; I actually thought it quite good.

Okay, Rod B. I should have said “beyond a reasonable doubt”. As for “a lot” thinner – Kwok, R., and D. A. Rothrock (2009) find “an astonishing decrease of 1.75 m in thickness”. I stand by what I said. A lot thinner.

“Kevin Stanley (91), the statements 1) …the overall distribution of ice thickness, which we have not been able to measure routinely in the past…, and 2)…data show beyond doubt that the ice is a lot thinner now than previously… are consistent with each other??? Could’ve fooled me! I wonder how much “a lot” is, especially “beyond doubt.””

‘Routine measurements of the overall distribution’ is simply a much higher standard than ‘enough data to confidently say there has been a large change.’

Even if you haven’t been able to measure something routinely and comprehensively, you may still have been able to get enough measurements of enough of the area of interest to confidently judge a big change.

And of course, this is in fact the case. For instance there’s the submarine data from the US Navy that Hank has mentioned. Is it enough to characterize as “routine” measurements of “the overall distribution of ice thickness” across the entire arctic? Nope. Is it enough to confidently conclude that arctic ice has been getting thinner? Absolutely.

Can you see it now? The statements do not conflict with each other at all.

Very nicely done summary of Arctic ice conditions over this past year. Thanks for taking the time to post it. I would like to hear a bit more about the frquency of the Arctic Dipole Anomaly, espcially as it affects the formation of sea ice, and the possible positive feedback loop that may be established where open water creates the conditions for high pressure, leading to more open water etc. I also know a great many of us are looking forward to the CryoSat 2 data with keen interest, as it will provide a valuable tool to really looking at the status of sea ice volume and mass.

These are anomalies with respect to the seasonal averages. According to some predictions, AGW is supposed to reduce total sea ice at each pole, so the seasonal total should decline.

66, dhogaza: That’s only a single time series, but it certainly is not evidence for global “warming”.
…
Ahem, it’s not evidence for uniform warming across the globe.

I prefer my locution: a constant time series is not evidence for any change. Of course, it may also not be evidence against some particular change, but the AGW predicts reduced ice at each pole, and disappearance of ice from some parts of Antarctica has been cited as evidence of AGW even as ice accumulated in other parts.

77, Stefan: [Response: The difference between Arctic and Antarctic sea ice response is explained on page 30/31 of the Copenhagen Diagnosis. It makes no sense to look at the sum of both, since they are affected by very different processes and their seasons are out of sync – when you look in northern summer, the Arctic is near its minimum and the Antarctic near its maximum, so the sum is simply dominated by the latter. -stefan]

A few years ago, global sea ice total was below average, and that was cited as evidence for AGW.

94, tamino: Anyone who suggest “the gradual increase of the extent the past few most recent years” as evidence against a significant long-term declining trend, just can’t be taken seriously.

I agree, but your message is a few years late. A rather prominent trend that ended in 2007 was widely cited as evidence for global warming, despite the fact that it was a short-term trend. It has been followed, apparently, by a regression toward the mean.

From April through June of 2010 Arctic ice melted at a higher rate than previously measured for that season, and got a lot of press. Since then, the Arctic ice has melted at a slower rate than previously measured for the month, and the message is it’s a short-term trend of no consequence.

But all of the short-term trends are of little evidentiary value, including the warm summer of 2010 on the American East Coast, and the cool summer of 2010 on the American West Coast. The long-term “trends” of temperature and precipitation on both coasts are nearly flat.

There is perhaps no single topic on which we hear more blathering idiocy than the subject of ice in general, and sea ice specifically — as this thread has already demonstrated.

I believe that the reason is this: the cryosphere is so obviously screaming “global warming” so loud, that denialists feel they have to say something, anything, no matter how false or how stupid, in a vain attempt to silence it.

“….some denialist is sure to notice this at some point and argue that the missing Arctic ice is countered by excess Antarctic ice…”

The first thing to point out is that less Arctic ice will mean more evaporation from open water and higher humidity in the North polar cell circulation, regardless of how much ice is in the Antarctic. The southerly surface flow of the polar cell will carry more moisture into the Polar/Ferrel cell uplift region, increasing precipitation. This may be observed in increased rainfall(or snowfall when the temperatures are low enough); it will be predominately in fall when decreasing temperatures are squeezing out the excess moisture built up by the larger summer ice extent decline. [2][3][4]

The second thing to point out is that any yahoo like me with internet access and a rudimentary spreadsheet can show that NH declines aren’t balanced by SH increases. [5] Note that yearly averaging hides the decline of the much larger summer versus winter season; a larger effect on the weather won’t be hidden.

NSIDC Reports That Antarctica is Cooling and Sea Ice is Increasing trumpets the observation that Antarctic sea ice is increasing. This is expected from climate modeling. Nice to see someone else is picking up on this interesting confirmation of our scientific expectation….

28 Wilt said, ” It seems to me that in this situation things like AMO are more important than CO2.”

In essentially all situations things like the AMO matter more than CO2, but CO2 changes the universe of potential situations. In other words, short-term weather stuff masks long term climate stuff over the short term.

These are anomalies with respect to the seasonal averages. According to some predictions, AGW is supposed to reduce total sea ice at each pole, so the seasonal total should decline.

Excuse me if I don’t fall into this typical denier trap.

“According to some predictions, AGW is supposed to…”

So you make a vague claim that a claim is sort of made, etc. etc.

Please cite a specific prediction, attributable to some work of science (not a blog or some vociferous denier’s recollection), with the source.

At the same time, please read the second paragraph from Hank’s link (#117):

The prediction is old. In 1992 Manabe and coworkers, in running a changing CO2 experiment, noticed that the Antarctic sea ice cover increased with increasing CO2. They traced this to increased fresh water on the Antarctic ocean, which derived from increased precipitation — snow. They also observed in their model that the Arctic ocean sea ice experienced a marked decline in thickness, and major loss of extent in the summer, but not so large a decrease in the winter.

Didactylos (110, how about, “we strongly suspect?” ‘Beyond a reasonable doubt’ is the highest level of proof in legal circles and not met here.

Quite a feat: with very few measuring capabilities your references none-the-less have measured the decreasing thickness within one centimeter — presumably as an average over the entire Arctic? Impressive! You’re still confusing extensive scientific measurements with strong personal beliefs based on a few observations.

Kevin Stanley (111), ‘enough data to confidently say there has been a large change’ is getting more like it, though I could still quibble a little bit with the elusive “large.” However, the initial phrases are still inconsistent: their words are not the same as these words. A scientist who says, “I’ve been looking at it a long time and from many perspectives, and, though I have little direct tangible evidence, I am confident from the evidence I do have that the ice is thinning to the extent that a major global problem is ensuing” is speaking like a scientist. I might disagree with his/her conclusions but I can’t refute his analysis. On the other hand one who espouses hyperbolic rabid rhetoric and claims evidence that clearly does not exist is not acting scientifically and I can state with confidence ‘beyond a reasonable doubt’ that he’s just blowing smoke up my butt.

Comments from Rod B and Septic Matthew are what I was talking about in #115.

If hairs are all they’ve got, hairs are what they’ll split. Failing having anything useful to say, semantic quibbling can fill any empty volume, even that which used to be properly filled with an icecap.

Chris, I may be mixing up things I heard about Callendar and Arrhenius? Some of what is in my head came form talking to different scientists and I don’t recall (oops, an Alberto Gonzales moment ;).

Here are a some of gems from Svantes paper in 1896:

“Certain American geologists hold the opinion that since the close of the ice age only some 7000 to 10,000 years have elapsed, but this most probably is greatly underestimated.”

“A simple calculation shows that the temperature in the Arctic regions would rise about 8º to 9º C., if the carbonic acid increased to 2.5 or 3 times its present value. In order to get the temperature of the ice age between the 40th and 50th parallels, the carbonic acid in the air should sink to 0.62–0.55 of its present value (lowering of temperature 4)–5) C.)”

“On the supposition that the mean quantity of carbonic acid in the air reaches 0.03 vol. per cent,”

“The following calculation is also very instructive for the appreciation of the relation between the quantity of carbonic acid in the air and the quantities that are transformed. The world’s present production of coal reaches in round numbers 500 millions of tons per annum, or 1 ton per km.squared on the earths surface. Transformed into carbonic acid, this quantity would correspond to about a thousandth part of the carbonic acid in the atmosphere”

RodB:perhaps it’s true that “one who espouses hyperbolic rabid rhetoric and claims evidence that clearly does not exist is not acting scientifically and I can state with confidence ‘beyond a reasonable doubt’ that he’s just blowing smoke up my butt.”

Please have a look if you haven’t already at Kwok and Rothrock 2009, consider PIOMAS, read some of the IPY reports on arctic sea ice, and then tell us to whom you are referring when you say “one who…claims evidence that clearly does not exist.”

You have been directed to evidence, yet you seem to be claiming it “clearly does not exist.” Think about that for a second.

When you’re done with that, maybe consider the irony of accusing someone else of being hyperbolic and calling them rabid in the same sentence.

#127–John, as you can now see from Edward’s link, you were quite correct that Arrhenius considered the human contribution. At the time, though, the effective timescale appeared to be centuries, and Arrhenius didn’t anticipate what we now call the “downside.” He had a tendency to use the adjective “genial” to describe warmer climates.

Even Callendar, I think, uses the phrase “deadly ice” in connection with global cooling.

The realization that warming, too, could be “deadly” probably didn’t begin to dawn until Plass, who I think says that warming could become a “problem” in the future. (Though I don’t think he knew yet at that point–’56?–how soon that future could arrive! He was alive–though experiencing declining health, I think–when Kyoto was signed, and lived till March 1, 2004.)

Didactylos (121), so if I can not prove it is not thinning, it must be thinning??!! If I can’t prove that a horse can not climb the oak tree, it is proven therefore that it can? This has gone from silly to ridiculous.

tamino (122), I think Notz’ post was very well done. My comments supporting some of the things he said is hardly “polluting” his post. The other posters who I’m arguing with and who discount what Notz said have to be the polluters. Go fuss at them.

Doug Bostrom (123), if pointing out exaggerated statements is hair splitting, that means science does not need to be precise and bloviating hyperbole is perfectly acceptable so long as, presumably, the scientist’s heart is in the right place. Nice!

Rod B: I didn’t ask for proof. I merely asked for any evidence at all. Evidence that it is getting thicker, evidence that there is no trend in thickness, evidence that the thinning is very slight – you have offered none of these.

If you provide some evidence, then we can weigh it against the strong evidence of severe long-term thinning, and make our own judgements.

Kevin Stanley (126), you are correct that I am not aware of all even many of the ice thickness studies. I am relying on just one source, Notz, in this thread when he says, “However, for [total sea-ice volume] estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.” So if you have sources that say Notz is flat-ass wrong and some have long been able to measure thickness over the whole Arctic to within one centimeter, it sounds not credible, but I certainty can’t refute it.

Please don’t raise the strawman that I’m saying Notz therefore does not believe diminishing sea ice volume is a problem. He doesn’t, and I have not said so.

John P. Reisman (127), good point. I am not disagreeing that many are confident that sea-ice volume in the Arctic is significantly shrinking, and, more to the point, some of those are studied scientists who are drawing a not unreasonable conclusion — maybe an irrefutable conclusion — with high confidence. I’m merely taking to task those that spout our super capability to make very accurate measurements of the sea-ice volume when that capability doesn’t exist.

BTW, in the battle for hearts and minds, those ballyhooed exaggerations just serve up fat slow pitches for skeptics and (gulp) deniers to blast out of here — DOES NOT help your cause.

Remote sensing of my cranium via mirror reveals a trend to more skin. In-situ digital inspection reveals that the volume of my hair is not increasing farther toward my personal upper pole. Invisible hair indeed appears to be a hint that loss is taking place. I conclude that my hair is “thinning,” a more comforting term than “I’m going bald.”

So are you saying that Spencer Weart lies about his age, and is in fact at least 91 years old, having had that conversation with Arrhenius in 1929 at the prodigal age of 10? Or are you implying that Weart (or maybe Arrhenius, or both) has a time machine?

[Sorry… the deniers get to quote mine all the time. I just wanted to try my hand at it.]

Rod B: How do you hope to have a sensible conversation about anything when you only look at one statement? You can examine it and tear it apart all day long – but until you look at the studies that Notz and I base our conclusions on, you will never understand why our claims are consistent.

It disturbs me greatly that you haven’t bothered to find out about the data our claims are based on. Notz, of course, references his own work. I have already pointed you to Kwok, R., and D. A. Rothrock (2009), and they in turn reference Rothrock’s earlier work, Rothrock et al. (1999, 2008).

Now, go and read at least the conclusions of these papers, and think for a moment about the difference in data quality between submarine cruises and satellite data. Next consider for a moment that currently we have neither real-time satellite data, nor real-time submarine data. Now do you understand what Notz meant when he said “at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.”?

It will take you a while to read and digest all this, so I will ignore you for at least 24 hours. Maybe tomorrow will lead to a more productive conversation.

Rod B says, ” I’m merely taking to task those that spout our super capability to make very accurate measurements of the sea-ice volume when that capability doesn’t exist.”

There is, of course, always the question of how accurate measurements must be to draw a conclusion about a general trend. If we see ice thinning everywhere we look, it begs credulity to think that it must be thickening everywhere else–particularly when we KNOW temperatures are rising. Sometimes, logic works, Rod.

OK, I’ll accept that AGW makes no claim that Antarctic ice will decline. I didn’t bookmark what I read (or else it was a few years ago), and it may have been an unreliable source. If I come across something good (i.e. peer-reviewed) in the future, I’ll post a reference. Until I read something different, I’ll accept what you wrote.

Slightly off topic, but does AGW predict increase tropical cyclone activity? NOAA predicted an increase in activity for this year, but so far that has not happened.

Extract from the third, based purely on simulations (and note that it is for a 3x CO2 increase, or somewhere around 855ppm, while we’re now only at 390ppm):

For 3 × atmospheric CO2 in that model configuration, the simulated tropical cyclones experienced a 56% increase in the number of storms with maximum wind speed greater than 30 m s–1 and a 26% increase in the number of storms with central pressures less than 970 hPa, with no large changes in frequency and movement of tropical cyclones for that southwest Pacific region.

There are many, many others. Use this link to search for “cyclones” in the IPCC report:

I’m pretty sure that a prediction by the NOAA on an individual year would have to do with specific conditions this year, however, without any vague climate change factor, and like all weather predictions…

I would expect, however, that any such increase related to climate change would have to go with a correspondingly strong increase in temperatures, and while it’s getting warmer (0.8C since 1979, give or take), I’d be surprised myself (again, not being a scientist, not looking at actual numbers, just eyeballing things) if the warmth we’ve seen so far could also be matched to any statistically measurable increase in either storm strength or quantity.

There’s just too much variability in the system, I think, to get anything useful out of that until (a) temperatures rise a lot more and (b) one has a much longer time frame in which to gather data.

But since the warming we’re committed to now (how ever long it takes to get there) is probably about 1.4C, and we’re unlikely to take reasonable action as a civilization until we’re committed to at least that magical 2C mark, then I expect we will know at least part of the answer to that question in time (whether we like it or not).

Right now that shows ice volume is somewhere below FOUR standard deviations below the ‘historic’ mean trend for this time of year. This is further from the trend than ever observed, and does not bode well for ice survival should wind and weather even briefly conspire towards minimising ice extent in October.

And Cryosphere’s present image shows more fragmented and lower ice concentrations for this time of year that I can recall from many years of watching.

Re #137: Just to amplify what Bob said, tropical cyclone forecasts for individual years have much to do with the detailed conditions for that year, not primarily AGW, since there is a lot of year-to-year variability. In particular, note that Bill Gray has also predicted a very active Atlantic hurricane season ( http://hurricane.atmos.colostate.edu/forecasts/ ) and he is an AGW “skeptic”.

The article states: ” Arctic ice…again and again in early summer the question arises whether the most recent trend in sea-ice extent might lead to a new record minimum”.

I imagine that other folks (myself included) are also looking at Antarctic ice reaching maximum’s, as it appears to have done recently. Do you think that this is worthy of a similar note? I’d be interested for one.

[Response: We ought to do that. I’ll look into it. A couple notes for starters though: First, Antarctic sea ice isn’t as predictable, because it is thinner, and more subject to winds. Second, huge areas of Antarctica have actually seen persistent declines in sea ice. The average trend has been positive, but barely so. In West Antarctica (where it is warming) the trend has been strongly negative.–eric]

\A much more useful measure for the state of Arctic sea ice is therefore the total sea-ice volume. However, for its estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.\

This website make exactly the opposite statement saying that the navy does measure ice thickness and that the total ice thickness has increased over the past 2 years:

Those crazy deniers! Models are wrong, they say. But when observations look inconvenient, suddenly the model is right and the observations wrong?

I’m sure PIPS2 is a useful product, but I give it as much credence as any weather forecast.

John McCone: Watts and friends have misled you to believe the navy measures ice thickness. They don’t. They put the concentration data into a computer model and try to forecast thickness. This is very, very similar to what PIOMAS does.

It took me a moment to work out exactly how Watts produced this rabbit out of a hat (never mind the meaninglessness of comparing two single days). But I got there after a pause for thought: firstly, he is looking at winter/spring ice, so we don’t see the unambiguous signal seen in late summer. Then, in early 2008 the ice was in poor shape having undergone extreme basal melting in 2007, due to the ocean heating caused by the open water associated with the dipole anomaly. 2007 also saw a huge loss of multi-year ice. In 2010, the proportions of first and second year ice were more normal – but that did nothing to stop it melting.

“This website make exactly the opposite statement saying that the navy does measure ice thickness and that the total ice thickness has increased over the past 2 years:”

1) As Gavin noted, short term trend
2) The PIPS method that Goddard uses is a combination of Navy data and Goddard’s own home-cooked system: the volume dataset used by most Arctic scientists seems to be the PIOMAS dataset, though even that system uses a number of extrapolations and therefore (as far as I can tell) is not as sound a dataset as sea ice extent.

We are told that the increased Antarctic sea ice extent we have seen was forecast and is entirely in line wth the Models and predictions. When exactly did this become the truth? It wouldn’t be another example of past posting would it?

I tend to find my predictions are pretty accurate when made after the event!

This is what the IPCC said about Antarctic sea ice in 2001.

“16.2.4.2. Sea Ice in the Southern Ocean
Antarctic sea ice is not confined by land margins but is open to the Southern Ocean. Sea-ice extent contracts and expands on an annual cycle in a roughly concentric zone around Antarctica. The ultimate extent is controlled by a balance of air temperature, leads, wind direction, upper ocean structure, and pycnocline depth. Some of these parameters are controlled in the atmosphere by the relative position of the subpolar trough with respect to the sea ice. In the ocean, variations in the Antarctic Circumpolar Current are important. The extent and thickness of Antarctic sea ice are sensitive to the depth and thermal properties of overlying snow, about which relatively little is known.

A reduction in Antarctic sea ice volume of about 25-45% is predicted for a doubling of CO2, with sea ice retreating fairly evenly around the continent (Gordon and O’Farrell, 1997). This CSIRO model assumes a 1% yr-1 compounding increase of CO2, corresponding to global warming of 2.1°C. Using a similar but modified model that has a higher albedo feedback and predicted global warming of 2.8°C, Wu et al. (1999) calculate a reduction in mean sea-ice extent of nearly two degrees of latitude, corresponding to 45% of sea-ice volume. These estimates do not represent the equilibrium state, and sea ice can be expected to shrink further, even if GHGs are stabilized.”

Here is what was said by the IPCC in 2007…………

” Highlights from the IPCC Working Group I Summary for Policymakers of “Climate Change 2007: The Physical Science Basis”

“What can we expect to happen?”…………..“Sea ice is projected to shrink in both the Arctic and Antarctic.”

Wind driven upwelling of water in a ring around Antarctica (in the midlatitudes or subpolar – I forget offhand which best characterizes it) can be enhanced by atmospheric responses to keeping the upwelling region SSTs similar while warming SSTs at lower latitudes; thus the upwelling can sustain itself and keep a latitude band in the Southern hemisphere from warming as much as other places. (Predicted)

The Southern hemisphere has less land area and thus the heat capacity of the ocean may slow hemispheric warming even more than in the Northern Hemisphere.

Antarctica’s ice sheet will tend to have a slower response time than sea ice and thus can prevent or delay polar amplification of the sort seen in the Arctic.

Alan Millar: I’m not aware of any specific prediction that Antarctic sea ice would continue its gradual increase in the short term.

As dhogaza says, in the long term, we do expect a significant decline.

So, what actually was expected?

We definitely expected to see the Arctic warm much faster than the Antarctic. Eventually, both poles will even out again, but that won’t be for a long time. Have a look at the climate model anomaly maps – they show this very clearly, and have done so from the beginning.

We are also unsurprised that increased precipitation should cause ice build-up in inland areas of Antarctica. This doesn’t compensate for the mass lost by melting, but in the recent past it has certainly caused regional mass gain. Many people confuse land and sea ice. Maybe that’s how the confusion started?

As far as I am aware, the dynamics of Antarctic sea ice are still an open question. There are some strong theories, but it’s not yet certain which mechanisms play how much of a role in the current increase. However, none of these theories will prevent the inevitable long term decline.